1. Field of the Invention
The invention relates generally to ethylene/α-olefin block interpolymers, dispersions of ethylene/α-olefin block interpolymers, and products made from the block interpolymers.
2. Background
Aqueous dispersions of a thermoplastic resin of various types are known in the art and have been used in a wide variety of fields. For example, when an aqueous dispersion is coated and dried on a surface of a substrate such as paper, fiber, wood, metal, or plastic molded article, the resin coating formed will provide the substrate with water resistance, oil resistance, chemical resistance, corrosion resistance and heat sealability. An aqueous medium is advantageous compared to an organic dispersion medium in view of common hazards such as flammability, working environment, handling convenience, and the like.
Conventional aqueous dispersions of a thermoplastic resin have been produced either by a process wherein a polymerizable monomer which is the resin raw material is polymerized by emulsion polymerization in an aqueous medium in the presence of a dispersing agent, or by a process wherein a molten thermoplastic resin and an aqueous medium, and optionally, a dispersing agent are mixed by applying shearing force. The former process is associated with the disadvantage of the limited number of the polymerizable monomers that can be used, and hence, the variety of the aqueous dispersions of the thermoplastic resin that can be produced, is limited. The former process also suffers from complicated control of the polymerization reaction as well as intricate equipment. On the other hand, the latter process is applicable to a wide variety of resins in relatively simple equipment.
Coatings and articles produced via aqueous dispersions of typical ethylene copolymers lack the heat resistance and compression set properties needed for many applications. For example, frothed foams made via the frothing and drying of aqueous dispersions of homogeneous ethylene-octene copolymers exhibit the softness required for hygiene and fabric backing applications, but lack the heat resistance required for shipment during the summer months. In addition, coatings and foams to be used in the interior of an automobile typically require heat resistance to at least 60° C. In this environment, frothed foams based on homogeneous, low crystallinity ethylene copolymers will not retain mechanical properties such as compression set.
Accordingly, there exists a need for dispersions and foams formed from ethylene and propylene based interpolymers having improved heat resistance and mechanical properties, including compression set.